Thermally controlled switch



J. F. FRESE THERMALLY CONTROLLED SWITCH April 28, 1936.

2 Sheets-Sheetl Filed May 11, 1935 Gum/mm Filed May 11, 1955 2 Sheets-Sheet 2 Patented Apr. 28, 1936 PATENT OFFICE THERMALLY CONTROLLED SWITCH Joseph F. Frese, Baltimore, Md., assignor to Monitor Controller Company, Baltimore, Md., a

corporation of Maryland Application May 11,

Claims.

This invention relates to a thermally operated circuit controlling device and particularly to a compensating air temperature responsive mechanism which will cause the operation of a switch 5- by a thermally responsive actuating element to be the same under all conditions of atmospheric temperature.

The type of thermally responsive element to which the present invention relates is that shown in patent to George H. Whittingham 1,627,816, dated May 10, 1927, comprising a flat, bimetallic strip helically coiled to form a tube or housing, this tube having one end open and secured to a suitable support while its other end is closed and free to turn. A heating element, comprising a part of the circuit controlled by the switch is inserted into the tube through its open end and the heat generated by the current in the heating element causes the tube to partly uncoil to operate a switch. This device is affected in its operation by the temperature of the surrounding atmosphere. In order to compensate for changes in atmospheric temperature, I provide in proximity to the tubular device just described, having a heating element, a similar bimetallic tube without a heating element so as to be affected only by the temperature of the surrounding air to compensate for changes in the thermally responsive tube resulting from such atmospheric temperature changes. This second tube is connected so that one end moves, in response to changes in atmospheric temperature, in unison with the free end of the first tube. As both are affected alike by atmospheric temperatures but are arranged in opposite senses, the distance between the operative elements will remain essentially uniform in spite of such changes in temperature, and only changes in temperature of the first thermally responsive actuating tube caused by the heating element therein will cause the operation of the switch.

In the accompanying drawings,

Fig. 1 is a front elevation of a circuit breaker embodying the invention, with manual re-setting means;

Fig. 2 is a vertical central section on line 2-2 of Fig. 1;

Fig. 3 is a plan view;

Fig. 4 is a transverse section taken on line 4-4 of Fig. 1;

Fig. 5 is a fragmentary plan view partly in section showing the arrangement of the twopart tripping lever and compensating thermal element:

Fig. 6 is a perspective view of the two-part 1935, Serial No. 21,054

tripping lever with a portion broken away to show the compensating thermal device;

Fig. 7 is a front elevation of a self-closing switch mechanism embodying the invention;

Fig. 8 is a section on the line 8-8 of Fig. '7, and,

Fig. 9 is a section on the line 9--9 of Fig. 7.

Referring to the drawings, I represents a suitable base of insulating material upon which the device is mounted. A and B indicate thermally responsive elements each adapted to operate a circuit breaking switch C. These elements are alike except that, being arranged on opposite sides of the switch, they are arranged to twist in opposite directions so as to operate the switch. The construction of both elements will be understood from a description of element B. This element comprises the tube 2 formed from a helically coiled bimetallic strip.

The base and the elements thereon are, in practice, arranged in an upright position, as shown. The lower end of each tube is fixed while the upper end is free to turn. Thus, as shown, the lower end of tube 2 is secured as by solder in an opening in the horizontal bracket 3 of a metal strap 4 which is secured to the base i. Through this opening a heating element 2 may be inserted into the tube and this element,

as shown, consists of a wire doubled "upon itself and having its ends secured to binding posts 5 and 6 to which terminals of an electric circuit may be connected. A metal cap piece I secured to the uppermost convolution of the tube 2 has a central opening and the guide pin 8, threaded into a second horizontal bracket 9 on the upper end of the strap 4, extends into this opening, preventing lateral displacement of the upper end' of the tube while permitting rotation thereof. The cap piece has a laterally projecting arm ID, at the outer end of which a flat insulating button H is secured for operating the two-part tripping lever D of the switch.

The element A is identical in construction with the element B except that the tube I2 is oppositely wound in respect to the tube 2 and the arm thereon extends to the right while the corresponding arm IU on the element 15 extends to the left in Fig. l. The buttons on these arms extend over upturned ends of respective furcations l3 and i l on tripping lever D for the switch C so that either element may operate the lever.

The switch mechanism C is normally latched in closed position and adapted to be opened by one of the elements A, B when heated by its coil. It comprises a fixed contact l1 and a movable contact I8. A metal plate I5 is secured to the central part of the base and has struck up therefrom an angled bracket l6 carrying on its outer face the stationary contact IT. The movable contact I8 is mounted on a broad spring |9 which is secured to the under face of a contact carrying lever which includes a flat plate 20 substantially parallel to the base and having at each side near its lower end ears 2| which embrace ears 22 bent up from the ends of a transverse metal strap 23 secured to the base. A pintle 24 pivots the respective sets of cars together and. a helical spring 25 surrounding this pintle and with opposite ends bearing respectively on the strap 23 and the under surface of the plate 20 normally holds the contact carrying lever in circuit opening position, the bent lug 26 on one ear 2| engaging the lower edge of an ear 22 to form a limit stop for the lever.

A downturned lug 21 struck out from the plate 20 passes through an opening in the spring l9 and a bent end 28 thereof is positioned beneath this spring to positively disengage the contacts by a hammer blow action in the event of sticking. The upper end of the plate 20 is turned up substantially at right angles as at 3|] and has a narrow vertically projecting latch 3| on its outer end. A suitable operating handle 32 permits manual closing of the switch contacts as will be obvious.

The switch shown is adapted to be held in restrained or closed circuit position by the two-part tripping lever D which engages the latch 3| for the purpose and which can be released from the latch by proper movement of either one of the buttons II, as heretofore explained. Obviously the tripping lever would operate equally as well to trip an appropriately arranged switch to closed position if desired.

The tripping lever D, which forms the essential feature of this invention, is in two parts, the first (1 comprising the. plate 34 having the latch receiving opening 35 in position therein to receive and hold the latch 3| of the contact carrying lever with this lever in circuit closing position. The plate is cut away as at 36 to clear the contact l1 and has formed integral with its lateral edges near the bottom thereof the ears 3! which fit between upstanding ears 38 on the metal plate l5. They are pivoted to these ears by the pintle 39 so that the plate 34 can be rotated in a clockwise direction from the position shown in Fig. 2 to release the latch 3|.

The second part (1 of the tripping lever includes the flat plate 4| from which the furcations l3 and I4 extend. The lower lateral edges of this plate are turned back to form the cars 42 which embrace the ears 38 on the plate l5 and are pivoted on the pintle 39. v

The two parts d and d of the tripping lever are mounted for independent movement about the same axis, but are connected together so as to move as a unit so that engagement of one of the furcations of the part 12 by one of the buttons under the influence of its thermally responsive tube when heated, will move the part d in order to trip the switch.

This connection takes the form of a helix 45 wound from a bimetallic strip which surrounds the pintle 39 and has one end secured to the plate 4| as at 46 by passing closely through a hole therein and being soldered or brazed thereto and the other end similarly connected as at 41 to the plate 34. This helix forms a strong connection between the two parts d, d of the tripping lever,

the whole assembly of which is biased in a counter clockwise direction as viewed in Fig. 2, to engage the latch 3l, when the latter is manually set by use of the handle 32, the biasing member being a light helical spring 48 surrounding the pintle 39 inside of the helix 45. One end of this spring rests on the plate l5 as shown at and the other end bears over one of the ears 3? as shown at 5|.

As viewed in Fig. 4, there is a clearance 52 between each button H and the upturned end of the corresponding furcation on the plate 4| of the tripping lever and it is desirable to maintain this clearance substantially uniform under all atmospheric temperature conditions. There will be a certain amount of movement of each button corresponding to atmospheric temperature changes which coil or uncoil the tubes of the thermally responsive elements A and B. These changes are compensated for by the thermally responsive helix 45 connecting the two parts of the tripping lever. The plate 34 of the one part (1 is held stationary by its spring-pressed engagement with the latch 3| and the base I so that changes in temperature which coil or uncoil the helix 45 produce a movement of the plate 4| and the integral furcations. The material of this helix 45 and its direction of wind are such that movement of the part d of the tripping lever in respect to the part d is commensurate with the movement of the buttons resulting from temperature changes of the surrounding air, so that the clearances 52 are maintained substantially constant at all times and the degree of lag in the operation of the switch under changes of temperature in either of the elements A or B resulting from heating by their heating elements, will be entirely independent of the temperature of the air surrounding the switch. Of course, the helix 45 is of sufficient strength to transmit movement imparted to the furcations on the plate 4| to the plate 34 with out appreciable lost motion so as to cause release of the latch 3| and opening of the switch contacts under the action or" the spring 25.

When the switch is set or closed by manual operation of the handle 32, the contacts I! and I8 engage'with a wiping contact and spring 48 causes plate 34 to snapthe spring 35 over the latch 3| on the movable contact carrying plate and hold the switch closed. Any changes in atmospheric temperature which cause movement of the buttons by the helices A and B tending to change the clearances 52 are compensated for by corresponding movement of the part d of the tripping lever under the action of the helix 45. If one of the heaters 2 is energized by an overload current, its coil A or B unwinds, closes the clearance 52 and the button engages the corresponding furcation l3 or M, moves the part d of the tripping lever and, through the helix 45,'the part d, thus drawing the plate 34 from the latch 3|, whereupon the switch snaps open under the action of its spring 25. After the element A or B which caused the switch to trip has cooled and its insulating button has moved out of engagement with the part d of the lever, the switch may be re-set by rocking the handle 32 upward, which will cause the latch or shoulder 3| to snap into the notch 35 in the part d. The part (1 will then be held stationary by its engagement with the latch while the part d will be free to move in response to atmospheric changes in temperature affecting the bimetallic helix 45.

In Figs. 7, 8, and 9, the invention is shown applied to a switch which is normally closed and which automatically closes after it has been opened by one of the elements A or B and after such element has cooled sufiiciently to allow of the return of the two-part lever. In these figures, the thermally responsive elements A and B and the heaters therefor are the same as in the preceding figures and are designated by corresponding reference characters. The lever D comprises the parts d and d pivotally mounted and connected together in the same way as the parts d and d of the lever D in Figures 1-6, inclusive, but the part (i in Figures 7 and 8,

instead of extending outwardly at an angle to the part d lies substantially parallel with the base and carries contacts 54 and 55 which normally engage stationary contacts 55 and 51, respectively, the latter contacts being terminals for the circuit which is to be controlled. The lever and the contacts thus form a switch C The'lever part 11 corresponds with the part d in Figs. 1-6, and the bimetallic helix &5 and spring it serve the same functions in both structures.

It is essential to the operation of the device that the part (1 of the lever shall be held against a stop by the spring '48 in order that the part (1 may be free to move when the thermal element 45 which connects them' coils or uncoils in response to changes in atmospheric temperature. The light coiled spring 48 constantly presses the part d toward the stationary contacts 56 and 577 which serve as stops for the lever as weli as switch parts co-operating with the contacts on the lever.

When an over=load current in one of the heaters causes uncoiling of the bimetallic helix A or B with which it is associated sufiiciently to cause the button i l to engage and move the twopart lever D, the switch C will be opened. The switch (3 may be, and ordinarily is, employed to control a contactor which opens the'circuit of which the heater is a part. After the current has been cut off or the abnormal flow of current through the heater has subsided, the coiling of the helix associated with theheat-er causes the button l i to move away from the lever and permit the latter to be moved by the spring at to the switch closing position.

What I claim is:

i. In a circuit controlling mechanism, a base of insulating material, a thermally responsive helix mounted thereon composed of a bimetallic strip having one end fixed and its other end free to turn and an arm projecting laterally from the latter end, a heater element adjacent said helix, switch mechanism mounted on the base adjacent said helix and comprising a two-part lever pivoted between its ends and a thermally responsive element firmly connecting said parts so that they may rock in unison in response to mechanical force and move relatively to one another in response to change in atmospheric temperature atfecting said latter element, said arm adapted to engage one part of the lever and rock the lever in the direction to actuate the switch when said helix is heated by said heater, and means biasing said lever in the opposite direction.

2. Circuit controlling mechanism comprising a base of insulating material, a thermally responsive helix composed of a bimetallic strip having one end fixed and its other end free to turn and an arm projecting laterally from the latter end, a heater element adjacent said helix, switch mechanism mounted on the base and comprising a lever movable by said arm to actuate the switch when the helix is heated by said heater, said lever com prising two parts and a thermally responsive ele-= ment firmly connecting said parts so that they will rock as a unit when moved by said arm and move relatively to one another in response to atmospheric temperature afiecting the latter helix, and a spring biasing said lever to switch closing position.

3. Circuit controlling mechanism comprising a base of insulating material, a switch mounted thereon, a thermally responsive helix composed of a bimetallic strip having one end fixed arid its other end free to turn and an arm projecting laterally from the latter end, a heater element adjacent said helix, a lever movable by said arm to actuate the switch when the helix is heated by said heater, said lever comprising two parts pivoted for independent movement about a common axis and a bimetallic helix co-axial with said axis and firmly connecting said parts so that they will rock as a unit when moved by said arm and move relatively to one another in response to atmospheric temperature affecting the latter helix, and a spring biasing said lever to switch closing posi tion.

4. Circuit controlling mechanism comprising a base of insulating material, a switch mounted thereon and comprising a stationary member and a movable member biased toopen position, a thermally responsive helix composed of a bimetallic strip having one end fixed and the other end free to turn and an arm projecting laterally from the latter end, a heater element adjacent said helix, a lever movable by said arm to actuate the switch when the helix is heated by said heater, said lever comprising two parts and a bimetallic helix firmly connecting said parts so that they will rock as a unit when moved by said arm and move relatively to one another in response to atmospheric temperature afiecting the latter helix, one of said parts extending into position to be engaged by said arm and the other part adapted to interlock with said movable switch member, and a spring biasing said lever to the interlocking position.

5. Circuit controlling mechanism comprising a base of insulating material, a switch mounted thereon, a thermally responsive helix composed of a bimetallic strip having one end fixed and its other end free to turn and an arm projecting laterally from the latter end, a heater element adjacent said helix, a lever movable by said arm to actuate the switch when the helix is heated by said heater, said lever comprising two parts and a bimetallic helix firmly connecting said parts so that they will rock as a unit when moved by said arm and move relatively to one another in response to atmospheric temperature affecting the latter helix, said lever being biased to switch closing position.

JOSEPH F. FRESF... 

